A memory card is used as a storage device in various electronic apparatuses such as a computer, a PDA, a digital camera, a camcorder and the like.
FIG. 1 is a view illustrating one surface of a conventional memory card.
Referring to FIG. 1, a memory card 10 includes a memory device mounted on a printed circuit board for the memory card. The memory device is a kind of semiconductor device. The memory device is covered by a resin molding unit. Furthermore, a terminal unit 11 is formed on one surface of the memory card to serve as a connector which is electrically connected to the electronic apparatuses in which the memory card 10 is used.
Meanwhile, the terminal unit 11 performs the function of the connector which is electrically connected to the electronic apparatuses of the outside.
When a defect such as a scratch or being stabbed is generated in the terminal unit 11, this has a large effect on a yield rate of the memory card 10.
FIG. 2a through 2h are cross-sectional views illustrating a conventional method of manufacturing a printed circuit board for a memory card in order of processes.
Referring to FIG. 2a, the printed circuit board for the memory card according to a conventional art includes a terminal unit 31 formed on a lower surface of the insulating layer 30, and a mounting unit 32 formed on an upper surface of the insulating layer 30. Even though the constituent element is not illustrated in FIG. 2a, the terminal unit 31 and the mounting unit 32 may be electrically connected to each other through via holes in which a conductive material is buried, thereby forming a circuit.
The terminal unit 31 provides the function of a connector so that the mounting unit 32 formed on the upper surface of the insulating layer 30 is electrically connected to external electronic apparatuses. The mounting unit 32 forms a circuit, mounts resistance, a capacitor and the like, or provides the function of a pad intended for an electrical connection with a memory device.
A photo-imagable solder resist 33 is formed at an upper side and a lower side of the insulating layer 30 so that each one part of the terminal unit 31 and the mounting unit 32 is exposed.
Referring to FIG. 2b, a first photosensitive dry film 34 is formed at the upper side and the lower side of the insulating layer 30, and the mounting unit 32 is exposed by performing an exposure process and a development process.
Referring to FIG. 2c, a soft gold layer 35 is formed on the mounting unit 32. It is advantageous in that the soft gold layer 35 enables gold wire bonding to be performed and has a good solder ability.
Furthermore, as illustrated in FIG. 2d, the first photosensitive dry film 34 is removed.
Referring to FIG. 2e, a second photosensitive dry film 36 is formed at the upper side and the lower side of the insulating layer 30, and the terminal unit 31 is exposed by performing the exposure process and the development process.
Referring to FIG. 2f, a hard gold layer 37 is plated with and formed on the terminal unit 31.
Since the hard gold layer 37 has high surface strength and high corrosiveness, the hard gold layer 37 is plated with a part which is frequently detached from other electronic apparatuses such as a connector of the memory card.
Referring to FIG. 2g, the second photosensitive dry film 36 is removed. Before the second photosensitive dry film 36 has been removed, to prevent the hard gold layer 37 from being damaged, a protective layer (not drawn) may be additionally formed.
If the processes as described above are all performed, the printed circuit board for the memory card may be manufactured. When the printed circuit board is manufactured, a memory semiconductor chip and a memory controller are attached thereto, thereby enabling it to be manufactured as the memory card.
That is, as illustrated in FIG. 2h, a memory device 40 is mounted on the photo-imagable solder resist 33 of the upper side of the insulating layer 30. The memory device 40 is electrically connected to the soft gold layer 35 through a wire 39. For example, the memory device 40 may be a memory chip or a memory controller.
Furthermore, that a molding member 41 is formed at the upper side of the insulating layer 30 in which the memory device 40 and the soft gold layer 35 are formed. The molding member 41 is formed by epoxy molding which is called an epoxy molding compound EMC so that circuit constituent components including the memory device 40 can be protected from external impacts or external environments.
However, with regard to the process of manufacturing the printed circuit board for the memory card according to the aforesaid conventional art, since properties required for the terminal unit 31 and the mounting unit 32 are different from each other, different gold plating processes from each other should be performed for the terminal unit 31 and the mounting unit 32. Thus, since various processes such as separate exposure and development processes and a process of peeling off a dry film should be carried out, it is disadvantageous in that economics and productivity is not good.